Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
Fig. 3 is the structured flowchart of the LED drive unit that provides of the embodiment of the present invention; For convenience of explanation, only show the part relevant to the present embodiment, as shown in the figure:
A kind of LED drive unit, AC is connected with AC power, comprise rectifier bridge B1, capacitor C 1 and adjustable LED load 100, as improvement, this LED drive unit also comprises: Logic control module 200 and the charge-discharge modules 300 joining with it respectively, voltage detection module 400 and NMOS pipe N1; Wherein, charge-discharge modules 300 and capacitor C 1 are attempted by after connecting between two outputs of rectifier bridge B1, the output of the control termination Logic control module 200 of charge-discharge modules 300, drain electrode and the LED load 100 of NMOS pipe N1 are joined, the grid control termination Logic control module 200 of NMOS pipe N1, the drain electrode of the input termination NMOS pipe N1 of voltage detection module 400 and LED load 100 connect altogether end; The output termination Logic control module 200 of voltage detection module 400.
In practical work process, the voltage height that voltage detection module 400 drains by detecting the NMOS pipe N1 of LED load 100 cathode end, output overvoltage signal OVH, under-voltage signal OVL and/or capacitor charging termination signal OVC are to Logic control module 200.Particularly, under the control of Logic control module 200, civil power input is charged to capacitor C 1 by the charging circuit in charge-discharge modules 300 through rectification output, when the capacitor charging termination signal OVC exporting when voltage detection module 400 is low level, be the voltage of NMOS pipe N1 drain electrode while also not reaching default high threshold, the charging circuit in charge-discharge modules 300 continues to open; In the time that the voltage of NMOS pipe N1 drain electrode reaches high threshold, the capacitor charging termination signal OVC that voltage detection module 400 is exported is just effective high level, and Logic control module 200 is at once according to this signal controlling charge closing circuit.Like this, Logic control module 200 can increase when a lot of at outside power network fluctuation, alternating current voltage, still can be in the time that rectifier output voltage be too high charge closing circuit, ceiling voltage in capacitor C 1 is maintained specifically on high threshold.Compare with prior art, make to be applied to the voltage and the dissipation power consumption that drive on chip and all diminish, realize high efficiency driving.
On the other hand, when rectifier output voltage is during lower than the voltage (high threshold) at capacitor C 1 two ends, capacitor C 1 is discharged to LED load 100 by the discharge circuit in charge-discharge modules.Further, in the time that the upper limit (being the high threshold of predeterminated voltage) of capacitor C 1 charging voltage is determined, the electric current that the lower limit of capacitor C 1 discharge voltage is crossed by size and the lamp crossfire of electric capacity itself determines, being greater than lamp string at the minimum voltage that ensures capacitor C 1 lights under the prerequisite of voltage, by control capacittance size, can adapt to the application demand of different lamp string streams.
To sum up, the LED drive unit providing according to the embodiment of the present invention, under the control of Logic control module 200, accurately the charging sequential of control capacitance C1 and electric discharge sequential, realize the greater efficiency of whole LED drive unit.
In the time of specific implementation, the LED drive unit that the embodiment of the present invention provides can also be as shown in Figure 4.Referring to Fig. 4, different from the LED drive unit shown in Fig. 3, there is exchange with the position of capacitor C 1 in charge-discharge modules 300.Although charge-discharge modules 300 and capacitor C 1 have been exchanged to position, the operation principle of whole device is the same, just repeats no more at this.
It is emphasized that the LED load 100 that the embodiment of the present invention is mentioned is generally adjustable LED lamp string.LED load 100 shown in Fig. 3 and Fig. 4 is one preferred embodiment.
Concrete, LED load 100 shown in Fig. 3 and Fig. 4 is connected in series formation by LED1～LEDn+1, and LED1～LEDn is in parallel with PMOS pipe P1～Pn respectively, and the grid control end of PMOS pipe P1～Pn connects respectively described Logic control module 200, and the cathode end of LEDn+1 connects the drain electrode of NMOS pipe N1.Overvoltage signal OVH and under-voltage signal OVL that Logic control module 200 is exported according to the voltage detection module 400 receiving, control the on off state of PMOS pipe P1～Pn, the quantity that changes the LED lamp string of lighting with this, approaches the voltage of voltage sum in LED load 100 and rectifier output voltage or capacitor C 1 electric discharge output.
When the overvoltage signal OVH exporting when voltage detection module 400 is high level, the overtension of the drain electrode of NMOS pipe N1 is described, Logic control module 200 will change the on off state of PMOS pipe P1～Pn, makes more lamp string light, carry a part of voltage, thereby makes overvoltage signal OVH become 0; In the time that under-voltage signal OVL is high level, the brownout of the drain electrode of NMOS pipe N1 is described, Logic control module 200 will change the on off state of PMOS pipe P1～Pn, lamp string is still less lighted, thereby made under-voltage signal OVL become 0.
The operation principle of the LED drive unit embodiment of the present invention being provided below by the drive waveforms figure under operating state as shown in Figure 5 further describes.Referring to Fig. 5, sinusoidal waveform is above civil power input waveform, drive waveforms figure when waveform is below the LED drive unit work shown in Fig. 3 or Fig. 4.Taking the drive waveforms shown in solid line in civil power input waveform as example.
Two horizontal dotted lines in drive waveforms figure are respectively Vth1 and Vth2.Wherein, Vth1 represents the minimum voltage that capacitor C 1 is discharged, and the magnitude of voltage summation that its value is generally the minimum lamp string of lighting in design is added the minimum voltage value (being mainly the conducting voltage of NMOS pipe N1) driving on chip; Vth2 represents the ceiling voltage that capacitor C 1 is charged, i.e. high threshold, and magnitude of voltage summation when its value is generally LED lamp string and all lights in design, adds certain voltage (conventionally getting between 6V～50V).In the T2 time period in the drawings, rectifier output voltage at Vth1 between Vth2, now capacitor C 1 is charged, Logic control module 200 is according to the overvoltage signal OVH and the under-voltage signal OVL that receive simultaneously, control the break-make of PMOS pipe P1～Pn, light the LED lamp string of suitable quantity, make voltage sum and the rectifier output voltage of the LED lamp string of lighting substantially approaching; Within the T3 time period, rectifier output voltage is higher than Vth2, and Logic control module 200 turn-offs charging circuit, stops capacitor C 1 to charge; Meanwhile, Logic control module 200, according to the overvoltage signal OVH, the under-voltage signal OVL that receive, is controlled the break-make of PMOS pipe P1～Pn, lights the LED lamp string of suitable quantity; In T4 and T1 time period, the absolute value of mains input voltage is less than the magnitude of voltage at capacitor C 1 two ends, and capacitor C 1 is discharged to LED lamp string.Because capacitor C 1 is discharged, rectifier output voltage constantly declines, and Logic control module 200 will, according to the overvoltage signal OVH receiving, under-voltage signal OVL, be controlled the LED lamp string of lighting suitable quantity equally.
Like this, only, within the T3 time period, due to rectifier output voltage higher (higher than high threshold Vth2), now the drive efficiency of whole LED drive unit is minimum; And at T1, T2 with in the T4 time period, because rectifier output voltage is between Vth1 and Vth2, can keep very high drive efficiency.Under normal circumstances, suppose that electric frequency is 50Hz, the duration of T3 time period is 2mS left and right, only account for 20% of the whole cycle, thereby the efficiency of T3 time period can reduce by 80% to the impact of drive efficiency in the whole cycle, so can realize high drive efficiency.
Drive waveforms when waveform shown in dotted lines in Figure 5 is line voltage rising.As seen from the figure, after line voltage raises, the duration of T3 time period is elongated, and T1, T2, the duration of T4 time period compare and shorten; Within the T3 time period, the efficiency of system is lower, at T1, T2, in the T4 time period, the efficiency of system is very high.Compared with traditional high-voltage linear constant current scheme, rectifier output voltage is only within the T3 time period, lifting more, and at T1, T2, in the T4 time period, rectifier output voltage changes very little, thereby can effectively weaken the impact that input line voltage raises on efficiency, in wider mains input voltage excursion, keep higher drive efficiency.
Further, as a preferred embodiment, LED drive unit provided by the invention can also comprise an adjustable current source I1.Adjustable current source I1 is arranged between the source electrode and ground of NMOS pipe N1.When the number change of the LED lamp string of lighting when Logic control module 200, the output of dynamic adjustments adjustable current source I1.General, can adjust according to LED lamp string total quantity and the proportionate relationship of the LED lamp string of lighting quantity the output of adjustable current source I1, in the time that the LED lamp string quantity being lit reduces, the electric current (being no longer that common constant current drives) that increases LED lamp cluster of lamps, ornamental core, the output size that can maintain like this luminous flux is approximate constant.
Fig. 6 shows three kinds of charge-discharge modules 300 in the drive unit of LED shown in Fig. 3 can embodiment.For convenience of explanation, only show the part being directly connected with charge-discharge modules 300.Specifically as shown in the figure:
In Fig. 6 a, charge-discharge modules 300 adopts NMOS pipe Nn as charging and discharging fulgurite; The grid of NMOS pipe Nn connects Logic control module 200, and the drain electrode of NMOS pipe Nn connects capacitor C 1, the source ground of NMOS pipe Nn.When charging, Logic control module 200 is exported high level and is opened NMOS pipe to the grid of NMOS pipe Nn, and electric current flows through the raceway groove of NMOS pipe to ground; Or Logic control module 200 output low levels, to the gate turn-off NMOS pipe of NMOS pipe Nn, make to charge to capacitor C 1 by NMOS pipe.When electric discharge, the diode current flow of NMOS pipe Nn parasitism, capacitor C 1 is discharged.
In Fig. 6 b, charge-discharge modules 300 comprises NMOS pipe Nn and is connected in parallel on the backward diode D1 between the drain-source utmost point of NMOS pipe Nn; The anode of backward diode D1 connects the source electrode of NMOS pipe Nn, and the negative electrode of backward diode D1 connects the drain electrode of NMOS pipe Nn, and the grid of NMOS pipe Nn connects Logic control module 200, and the drain electrode of NMOS pipe Nn connects capacitor C 1, the source ground of NMOS pipe Nn.Compare with Fig. 6 a, a backward diode D1 in parallel between the drain-source of NMOS pipe Nn, can eliminate electric discharge time on from its parasitic diode overcurrent on the unlatching of NMOS pipe itself the impact of turn-off characteristic.
In Fig. 6 c, charge-discharge modules 300 is on the basis of Fig. 6 b, has increased a diode D2 between drain electrode and the capacitor C 1 that is connected to NMOS pipe Nn; The anode of diode D2 connects capacitor C 1, and the negative electrode of diode D2 connects the drain electrode of NMOS pipe Nn.Charging circuit as shown in Fig. 6 c is made up of NMOS pipe Nn and diode D2, and discharge circuit is made up of backward diode D1; Particularly, when charging, Logic control module 200 is exported high level and is opened NMOS pipe to the grid of NMOS pipe Nn, and backward diode D1 oppositely ends, and electric current flows through diode D2 and NMOS pipe Nn arrives ground; When electric discharge, diode D2 oppositely ends, and electric current flows through backward diode D1.
In addition, three kinds shown in Fig. 6 in can embodiment, can be connected in series a current-limiting resistance R1 between the source electrode of NMOS pipe Nn and ground again, the rush of current when discharging and recharging gently.
Fig. 7 shows three kinds of charge-discharge modules 300 in the drive unit of LED shown in Fig. 4 can embodiment.Same, for convenience of explanation, only show the part being directly connected with charge-discharge modules 300.Specifically as shown in the figure:
In Fig. 7 a, charge-discharge modules 300 adopts PMOS pipe Pm as charging and discharging fulgurite; The grid of PMOS pipe Pm connects Logic control module 200, and the source electrode of PMOS pipe Pm connects the output of rectifier bridge B1, and the drain electrode of PMOS pipe Pm connects capacitor C 1.When charging, Logic control module 200 output low levels are opened PMOS pipe to the grid of PMOS pipe Pm, and electric current flows through the raceway groove of PMOS pipe to ground; When electric discharge, the diode current flow of PMOS pipe Pm parasitism, capacitor C 1 is discharged.
In Fig. 7 b, charge-discharge modules 300 comprises PMOS pipe Pm and is connected in parallel on the backward diode D3 between the drain-source utmost point of PMOS pipe Pm; The grid of PMOS pipe Pm connects Logic control module 200, and the source electrode of PMOS pipe Pm connects the output of rectifier bridge B1, and the drain electrode of PMOS pipe Pm connects capacitor C 1.Similarly, charging circuit is PMOS pipe Pm, and discharge circuit is backward diode D3.Compare with Fig. 7 a, a backward diode D3 in parallel between the drain-source of PMOS pipe Pm, can eliminate electric discharge time on from its parasitic diode overcurrent on the unlatching of PMOS pipe itself the impact of turn-off characteristic.
In Fig. 7 c, on the basis of Fig. 7 b, increase a diode D4 between drain electrode and the capacitor C 1 that is connected to PMOS pipe Pm; The negative electrode of diode D4 connects capacitor C 1, and the anode of diode D4 connects the drain electrode of PMOS pipe Pm.Charging circuit is made up of PMOS pipe Pm and diode D4, and discharge circuit is made up of backward diode D3.
NMOS pipe Nn is similar with adopting in Fig. 6, in the charge-discharge modules 300 that Fig. 7 provides, between the PMOS pipe source electrode of Pm and the output of rectifier bridge B1, can be connected in series equally a current-limiting resistance R1 again.
Finally, the embodiment of the present invention also provides a kind of LED light fixture, and described LED light fixture comprises the LED drive unit under arbitrary form as previously mentioned.
LED light fixture provided by the invention and LED drive unit thereof, the result of the voltage detecting of the NMOS pipe N1 drain electrode according to voltage detection module to LED load cathode end, voltage on control capacitance C1 is no more than default high threshold, to improve the drive efficiency of LED drive unit.Particularly, under the control of Logic control module, civil power input is charged to C1 by the charging circuit in charge-discharge modules through rectification output.In the time that the capacitor charging termination signal OVC of voltage detection module output is low level, the voltage of NMOS pipe N1 drain electrode is not while reaching high threshold, the charging circuit in charge-discharge modules is opened; Otherwise charging circuit cuts out.Like this, can be in the time that rectifier output voltage be too high, charge closing circuit, the voltage maintaining in capacitor C 1 is specific voltage (being the high threshold of predeterminated voltage).When rectifier output voltage is during lower than the voltage (high threshold) at capacitor C 1 two ends, capacitor C 1 by the discharge circuit in charge-discharge modules to LED load discharge.In sum, under the control of Logic control module, the accurately charging sequential of control capacitance C1 and electric discharge sequential, to realize the higher drive efficiency of whole LED drive unit.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, although the present invention has been carried out to more detailed explanation with reference to previous embodiment, for a person skilled in the art, its technical scheme that still can record aforementioned each embodiment is modified or part technical characterictic is wherein equal to replacement.All any amendments of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.